Your boy has experienced a trauma. He may be avoiding you or trying to hide in general. I would try to find a way to try and make his aquarium a little safer so that he doesn't get stuck again.
I would also do as Luimeril suggested and spend time by his tank every day. He should warm up to your presence eventually. You may also just have a skittish betta. Other than a cave, if his aquarium looks a little bare, trying adding some silk or live plants. Bettas like to have areas to explore and hide and/or rest in.